Shelled protozoan. Light micrograph of a shelled protozoa, Peneroplis pertusus, belonging to the order Foraminifera. The living cytoplasm of the organism can be extruded in the form of false feet (pseudopodia) through pores in the spiral shell. The pseudopodia are used both for movement and the capture of food. Foraminifera protozoa are mostly marine; some are sea bottom dwellers whilst other form part of the surface plankton. The shells of Foraminifera creatures which lived in previous geological ages have been compressed and are now major constituents of chalk and limestone rocks. Magnification unknown.